Doujutsu
by JayTang
Summary: A short summary of pondering the possibilities and theories of doujutsu kekkei genkai.


**A/N: These ideas have been floating around in my head for a while.**

**It would be nice if Naruto had an IQ above the single digits in Canon.**

**11/30/10: Fixed it. The spelling and grammar was atrocious.**

**5/20/10**

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**Doujutsu**

Doujutsu, literally meaning "eye techniques", are generally the result of a kekkei genkai, and as such are genetic. Konoha has the rare advantage of having all known heritable doujutsu, barring the Rinnegan. Doujutsu, as their name states, result in the bearer having special eyes. A doujutsu may allow one to predict enemy movements, see through walls, catch glimpses of the future, or see chakra. Some ninja theorize that a person with a doujutsu actually has a physically different eye structure; for example the famed Byakugan of the Hyuga Clan in Konohagakure no Sato can pick up wavelengths of light that ordinary humans cannot perceive, allowing the Byakugan to see through solid objects and see chakra.

More interesting to note is the fact that people with doujutsu may have different connections between their optic nerve and their brains. Most people's visual information travels directly from the optic nerve to the occipital lobe of the brain. A person with a doujutsu would have an exponentially different brain structure, particularly in the areas dealing with vision, due to the amount of neural visual information they had to process.

When a Hyuga body was once dissected, it's Byakugan useless due to a Curse Seal, it was revealed that the corpse's occipital lobe was nearly twice the size of an ordinary human's. Kumo-nin theorized that this was due to the nearly 360 degree vision a Hyuga had with the Byakugan. An ordinary person would not be able to process so much information; the sheer amount of information would overwhelm the brain, possibly leading to catatonia or damaging the occipital lobe. However, it is unknown if a Hyuga is born with such a trait, or if it begins to develop as a young child first activates his or her Byakugan and gradually becomes accustomed to it.

The Sharingan, for example, is not just directly connected to the occipital lobe, but also to the hippocampus and the cerebellum. This accounts for the Sharingan trait of being able to instantly memorize anything the user sees. However, mild overstimulation of the hippocampus is known to cause apathy, irrationality, and sudden bouts of senseless anger, while major overstimulation causes depression, schizophrenia, rage, and senseless bloodlust. Overstimulation of the cerebellum causes paranoia, madness, and a general loss of sanity. Therefore, it is logical to assume that a person who uses the Sharingan on a regular basis will have excess stimulation in the aforementioned parts of the brain, causing symptoms to gradually appear over time. As time passes and the Sharingan is used over time, symptoms will theoretically worsen until the individual in question cannot be tolerated in safe society, and must be locked up to avoid harming himself or others. However, Konoha does not adhere to these policies, and unlike the other four ninja Hidden Villages, believes that the Sharingan, just like the Byakugan, has no ill effects.

In fact, none of the other Hidden Villages wanted to accept the Uchiha during the time when the Uchiha was a wandering clan. Even in the earliest records of history, Uchihas were shown to have had a habit of suddenly killing his or her best friend or allies. Obviously, this did not make for a desirable addition to a hidden village, and so the Uchiha remained villageless until the Shodaime Hokage invited them into Konoha. In fact, the Uchiha remained outcasts outside of Hi no Kuni **(The Land of Fire)**. During the Kumo incident with Konoha, they preferred to attempt to steal a child of the Byakugan, whose members had a much lesser rate of suddenly killing family members or friends at random. Also, Hyuga had their Byakugan at birth, and close to 100% of all Hyuga activated their doujutsu by the age of 20. On the other hand, less than 10% of all Uchiha activated their doujutsu throughout their entire lives, as they needed an incredibly life-threatening event to activate their Sharingan, and then they needed to survive through said life-threatening event. If Kumo were going to steal a doujutsu, they were going to steal a reliable one, damn it.

There have always been many rumors of other doujutsu, but such rumors are generally ignored because of lack of proof or lack of importance. A ninja clan who could tell what type of animal a given meat came from just by looking at it, without tasting or smelling it, would be useless to everyone (except perhaps the Akamichi).

Over time, humans have begun to make inferences about the nature of doujutsu. As compiled by the Niijudaime Hokage, a short summation of Konoha's three doujutsu is as follows:

_Among the three exalted Doujutsu of Konoha are the Sharingan, the Copy Wheel Eye, the Byakugan, the White Eye, and the Kokugan, the Black Eye. Each is unique in its own way, and although it may be considered presumptuous of me, the emotions and feelings associated with each._

_The Sharingan, considered extinct with the death of Sasuke Uchiha (as the unaging Madara Uchiha became sterile when he achieved immortality), can be called a selfish eye. It can only be activated out of intense fear for one's own life created by an intense, life-threatening situation. When activated, the user's iris turns red, and a single black tomoe orbits the pupil. As the Sharingan matures, more tomoe will be added for a maximum of three in each eye. The Sharingan gives the user four abilities. First, the Sharingan can see chakra flow, although not nearly as close to the extent of the Byakugan or the Kokugan. Said chakra must also be already in use; only the most skills of Sharingan wielders can see the chakra within a person's body, and no Sharingan can see the natural chakra nodes known as tenketsu. Second, the Sharingan grants enhanced perception; the user can perceive incredibly fast movement as if it were at normal speed (however, the user's body still moves at the same speed). Third, the user gains the ability to instantly copy any physical movement seen. This is extremely useful in the copying of handseals and taijutsu techniques, but is useless against pure chakra usage that requires no handseals, such as the Rasengan or the Juken. Lastly, the Sharingan has the power to plant mental suggestions in others with mere eye contact. It should be noted that this is not perfect mind control, a strong-willed individual can overcome the mental suggestion or a person with strong morals would not succumb to the sudden urge to murder or rob. Against a weak-willed person, however, a skilled Sharingan user can manipulate others like a puppet master and his puppets._

_However, there is an even darker side to the Sharingan. As I have said before, the Sharingan is a selfish eye; it is only activated for one's own self. A person can gain a heightened form of the Sharingan, raising it from its three-tomoe state in to the Mangekyo Sharingan, by a very dark deed. A person must kill his or her best friend, and feel the emotions stemming from the loss. This is the highest form of hypocrisy. A sane person cannot kill his or her best friend, if that is truly the case. If you kill someone for the sake of power, you are valuing power much more that that person's life, and one cannot consider a friend worth less that power. If you are truly willing to kill someone and have the audacity to feel regret, that person is not a friend. Over time, hundreds of Uchiha have murdered their comrades, family, and allies in the hopes of attaining a Mangekyo Sharingan, but almost all have failed due to lack of true friendship or lack of the emotion of sincere loss. _

_Among the civilians of Konoha, the Uchiha have long been glorified, primarily due to the clan's association with the Senju. The Uchiha have often been said to represent the ninja among the civilians: cool, collected, and ruthless. However, among the other shinobi of Konoha, the Uchiha have been disliked and even hated since their inception into the Konoha ranks. The largest reason for this is that if there was an Uchiha on a ninja squad, he would invariably copy the techniques of his teammates. No shinobi appreciated their original creations being stolen; it was a mockery of dedication and hard work. Naturally, Uchihas did not have many friends among other ninja; one simply does not steal from one's friends. Also, Uchiha ninja are generally described as egotistical and apathetic to the plights of others; not a good combination one wants in a person watching one's back in a life-or-death situation. Lastly, for the few who were friends (or psycophants) of the Uchiha were prone to suddenly being murdered for no apparent reason. Therefore, within a few generations of the Uchiha joining Konoha, the clan had no friends, nor did anyone want to be their friends. However this changed shortly after the Uchiha Massacre, people easily forgot such stereotypes and told themselves that Sasuke Uchiha, the sole survivor, would bring about a new, great, revolutionary Uchiha Clan. It should be noted that Sasuke did not deviate from his clan's tradition by much. My esteemed ancestor, the Rokudaime Hokage, personally ended the life of the last Uchiha for treason, mass murder, conspiracy to commit mass murder, and conspiracy to destroy Konoha._

_The Kokugan, on the other hand, can be considered a selfless eye. A person with this kekkei genkai can only activate the Kokugan under a very strict condition: the bearer's best friend or lover must die in front of his or her eyes, and the bearer must be willing to enact vengeance and justice, even at the cost of his or her own life. Only for the sake of another in this manner can the Kokugan be activated. Similar to the Sharingan, however, the Kokugan can be used at any time after it is unlocked. Interestingly enough, it is possible for a single person to have both the Kokugan and the Byakugan. As the Byakugan is a retina-based ocular kekkei genkai and the Kokugan is a pupil-based doujutsu, it seems that their physiological effects are different enough that they are compatible, unlike the iris-based Sharingan and the retina-based Byakugan. However, I digress._

_The activated Kokugan gives the appearance of the user's iris being a pure black, when in reality the pupil is simply expanding to cover up the iris. For those who have not seen it before, it appears as if the user has suddenly succumbed to Mydriasis as a result of drugs or underlying illnesses. However, the opposite is true, the user's body has not suddenly weakened; instead, the user's body has been revitalized._

_Similar to the Sharingan, the Kokugan allows the user to perceive his or her surroundings in slow motion. Unlike the Sharingan, however, individuals with the Kokugan can move exponentially faster with their doujutsu activated than without. This is a result of mass amounts of adrenaline and other hormones being released through their bodies. Indeed, every documented individual with the Kokugan has an endocrine system with capabilities far beyond that of a normal human. Also, their muscle fibers and nervous system are different than that of a shinobi's of equal muscle size, allowing quicker movements and speed without excess damage to body tissue._

_The Kokugan bears traits of the Byakugan as well. When activated, it gives the user approximately 315 degree vision, leaving a hole pointed almost straight back. Also, the Kokugan can see chakra, although not as well as the Byakugan, but far better that the Sharingan. However, the Kokugan can see all 361 tenketsu on the human body, like the Byakugan, so a Kokugan user could theoretically use the Juken style of fighting just as well as a Byakugan user could._

_In fact, the first bearer of the Kokugan was Kage, no last name. He was also known as Kage no Akanami, Kage Hyuga, and the Hyugakage. History records him as the surrogate brother to my esteemed ancestor Naruto Uzumaki-Namikaze, original jinchuriki of the Kyuubi no Kitsune and founder of Konoha's Golden Age. Although the circumstances in which Kage awakened his Kokugan for the first time is unknown, he was first recorded using the Juken at the Chunin Exams in the year 0013 EAK. He later married into the Hyuga Clan of Konoha. Once again, it appears I digress._

_Later, Hikaen Hyuga seceded from the Hyuga Clan and formed the Chuseiryu Clan, breaking off of the Hyuga Clan with the Clan Head's blessing. None of Hikaen's children inherited the Byakugan, but all retained the latent ability to awaken the Kokugan. Due to his family having very close ties with the Namikaze Clan, and coupled with amazing feats performed in the Fifth Great Shinobi World War, the Chuseiryu Clan soon became one of Konohagakure no Sato's prominent clans. As generations passed, its members rose from three to over three hundred. For those who know what to look for, it is easy to locate a Chuseiryu among Konoha's ninja ranks. Although not all Chuseiryu activate their Kokugan, they all work to gain the same, toned muscle structure, and all have distinctive dark colored eyes, usually dark brown or dark green. However, they are the best friends you can possibly make, and the worst enemies you can ever have. If you ever are teammates with and make friends with a member from the Chuseiryu Clan, you have made a friend for life. He or she will scrap the mission, ignore any protocol, and mutiny against a superior to protect a comrade (and more often than not, somehow still complete the mission.) If you make a true enemy of a Chuseiryu, do not expect to live another week._

_The Chuseiryu are generally seen as an eccentric but loved Clan. Interestingly enough, many describe feeling an "animal magnetism" towards Chuseiryu of the opposite gender. Like the Hyuga and late Uchiha, the Chuseiryu all have relatively similar personalities. The typical Chuseiryu is often soft-spoken, and cares little for glory, riches, or the opinions of others. Trust does not come easily to a Chuseiryu, and they are often socially awkward. Chuseiryu are generally liked among the ninja ranks, due to their loyalty to their teammates. The few Chuseiryu who have awakened their Kokugan are often very withdrawn, due to their best friends or lovers being murdered before their very eyes, but become incredibly powerful ninja due to their awakened blood limit. However, every single recorded Kokugan user has been known to have said that their new power was not worth the cost, in some way. Overall, none would disagree with the fact that the Chuseiryu Clan is a major player in Konoha's shinobi affairs._

_In fact (I seem to be breaking the Fourth Wall fairly often. Oh well), I met Akarui Hyuga in the Fox District Ninja Academy. We had what one would call an antagonistic rivalry, in our adolescent minds we were enemies, and were each constantly trying to beat each other in everything. After graduation, we were even placed on the same team, much to our mutual dismay! However, I remember our first B-Rank Mission. We were hired to protect a blacksmith from a local gang, a joint mission with two other teams. In the middle of a fight, I slipped in a puddle of blood, and my three opponents were about to kill me. I tensed, ready to take at least one of them out in my death throes, but Akarui rescued me. He scoffed, saying "You owe me one." and jumped back into the fight. Later in the fight, he was pinned to the ground with a spear through his stomach. I fought and guarded him, fighting off several enemies at once, so that our medic could come and heal him._

_After that fight, somehow we became best friends. Actually talking to each other for a change, we discovered we actually had a lot in common. To this day, we remain close friends, even though I'm the Hokage and he's the Jonin Commander._

_Oh, and one more thing about the Chuseiryu. Never, ever, EVER, insult his or her spouse/fiancée/romantic partner, unless you have a deathwish. The Chuseiryu are big on upholding their partner's honor, so calling a Chuseiryu's man's wife a whore is a fantastic way to have your genitals chopped off, a centimeter at a time (even if you are a woman. I saw it happen once, and it was the scariest shit I've ever seen.). Inebriation is no excuse. It also works the other way, too. Akarui's wife, Hikari Chuseiryu (who incidentally was also born a Chuseiryu, her and Akarui were only related if you went back dozens of generations), once heard Akarui complaining about a prostitute at our local bar who wouldn't leave him alone no matter how many times he said no. You wouldn't believe how much panic a skeleton lying in the middle of the street causes._

_You wouldn't believe the amount of paperwork I had to fill out to settle that incident. Anyways, Chuseiryu are quite possessive of their spouses. If you want to not be killed in a horrific fashion, don't fuck with a Chuseiryu. Even if you're also a ninja, don't think you're enough of a badass to pull it off; the Chuseiryu specifically train to maximize speed, and often utilize eloquent bladework in their fighting styles to compensate for a possible difference of strength for a physically stronger opponent. Any Chuseiryu, even without a Kokugan, becomes little more than a blur when moving at top speed. It is fortunate that the Chuseiryu are generally unconcerned with the affairs of the material world. Five platoons of twenty Chuseiryu each is probably enough to take over a small country. _

_That's about all I can say about the Chuseiryu and the Kokugan._

_Lastly, the Byakugan is the doujutsu kekkei genkai of Konoha's oldest clan, the Hyuga. Most Hyuga children activate the Byakugan around the average age of 6. The Byakugan appears to be a pupil-less iris that is grey, silver, lavender, bluish, or other soft colors, although some famous figures such as Hikaen Hyuga have been known to have unusual colors such as light brown. When activated, the eye appears the same, but the user gains visibly raised blood vessels, nervous tissue, and chakra meridians around the temples and sides of the eyes. The Byakugan gives the user nearly 360 vision, with only a small hole in the back pointing upwards. Also, the Byakugan has the most efficient chakra sensing of all the doujutsu, allowing the user to see the chakra network and the 361 tenketsu in the human body. Lastly, the Byakugan gives the user the ability to see through almost all solid objects within the range of their enhanced range of vision. While the maximum distance most Byakugan can see is 2500 meters, or 2.5 kilometers, famous ninja such as the Lady Hinata Hyuga was said to have a range of over 20 kilometers._

_It is the chakra and tenketsu seeing abilities of the Byakugan that allow them to use their devastating taijutsu style, Juken, the Gentle Fist. By attacking the chakra network, they can do anything from temporarily paralyzing someone to causing massive damage to the internal organs. With a single, light brush to the chest, a skilled Juken user can stop a person's heart. Even more dangerous in the shinobi world, by closing the tenketsu on the human body, a Hyuga can temporarily rob a ninja of the ability to perform ninjutsu or use chakra. Alternately, however, more benevolent uses of the Juken are deep-tissue muscle-relaxant massages (I love my wife), and stimulation of the internal organs to promote healthy organ systems. In fact, a Hyuga who is skilled in medicine can perceive the minute fluctuations in the human body that may warn of impending illnesses, strokes, heart attacks, or cancer._

_Also, the Hyuga Clan has a very interesting history. Since the beginning of the Clan up until the year 17 EAK, the Hyuga was separated into the Main Family and the Branch Family. All members of the Branch family were branded with the Caged Bird Seal at the age of 4. The seal was originally intended to protect the secrets of the Byakugan by sealing it away at death, but degenerated into a tool of oppression the Main Family used to keep the Branch Family in line. By threat of mind-numbing pain or instant death, the Branch Family was doomed to forever serve the Main Family._

_However, in the year 17 EAK, young Clan Head Hinata Hyuga declared the Caged Bird Seal morally unjust. With the help of Seal Grandmaster Kage, first bearer of the Kokugan, she removed the Caged Bird Seal from every member and had every member, including herself and her husband, sealed with the Freedom's Flame Seal._

_The Freedom's Flame Seal was designed for several main functions. One of the main functions the Freedom's Flame Seal retains is that it also seals the Byakugan away at death, preventing enemy ninja from taking viable genetic material from a corpse and breeding children with the Byakugan. However, the new seal also allows a person to temporarily seal away his or her Byakugan, if he or she fears impending capture but not death. A person with the Byakugan such sealed can have their natural kekkei genkai restored merely by returning to the Hyuga Compound and having a secret jutsu applied to them by the Clan Head. Thus, it is physically impossible to steal the Byakugan through invasive methods. However, the Freedom's Flame Seal does even more._

_Theoretically, a Hyuga kunoichi could be captured and raped, and if she became pregnant her child would have the Byakugan. Also, inbreeding within the Hyuga Clan was becoming a problem, as cousins were marrying each other to 'preserve the Byakugan'. Along with the new changes in Hyuga society, Hinata Hyuga also allowed Hyuga to marry outside of the Clan if they so wished, or others could marry into the Clan. A Hyuga woman sealed with the Freedom's Flame Seal will bear ordinary children without the Byakugan unless her lover also bears the Freedom's Flame Seal. Similarly, the children a Hyuga man sired would not have the Byakugan unless his lover also bears the same seal. In this manner, people can marry in and out of the Hyuga Clan without fear of the Byakugan's sanctity being compromised. Also, enemy villages will not be able to obtain the Byakugan in the unfortunate event that they are somehow able to capture a Hyuga for breeding purposes._

_Before this structural revolution, the Hyuga was a very rigid and formal Clan. Its members were cold and aloof, and often even arrogant and narrow-minded. Since the myriad changes Hinata Hyuga implemented, the structure of the Hyuga Clan has become much more relaxed. Socializing outside of the clan is encouraged and developing new techniques instead of allowing old skills to stagnate is widely promoted. With the lack of dress code (the former Hyuga Clan policies dictated a mandatory one); the only way to determine if one is a Hyuga is by their pupil-less eyes. Now, modern generations of Hyuga are among the friendliest ninja you will ever meet (assuming you are their allies. If you are not, you will find your internal organs starting to malfunction). From birth, Hyuga are taught the importance of having strong family bonds and the importance of friends and allies, a strong contrast to the former teachings of duty and fate that was the hallmark of past Hyuga education._

_Anyways, what most ninja visualize when they think of a Hyuga is a smile. Most have very sunny dispositions, much like their surname would suggest. However, their loyalty to their friends and family is rivaled only by the Chuseiryu._

_One thing to note is something that has not changed in the Hyuga's history: Hyuga women are scary. Apparently, there is a secret Juken technique that all Hyuga kunoichi are taught. I'm not sure of all the details and specifics, but it seems that the chakra network of a human male can be temporarily altered to prevent Nitrogen Monoxide from reaching the extremities of the body. In other words, if you piss off a Hyuga woman, she can make it so that you can't get hard for up to six months. (Some men claim for it to last five years, but I personally believe that is because they're just not getting any. My wife's never done it to me, thank the Kami.)_

_Of the three doujutsu of Konoha, only two survive to this day: the Byakugan and the Kokugan._

The journal ends here.

**A/N: eh? Well what did you think? As you can tell, the facts in here are based loosely off my story ****The Demon Brothers of Konoha****.**

**Well, read and review, and I might add more soliloquies on concepts in the Naruto world!**


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